“…Here the first integral is the total mass of bacteria and P is the so-called Preisach operator [28] with the time dependent density function u; differential equations with the Preisach operator have been studied, for example, in [5,43,2,9,4,12,11,25,24,23]. Further, we replace the unknown functions f 1 and f −1 in system (2.1) by v = f 1 + f −1 (total mass of the two nutrients) and w = f 1 /(f 1 + f −1 ) − 1/2 (deviation of the relative concentration of the first nutrient from the value 1/2).…”